Supplementation of protein diets with di- and tripeptides

ABSTRACT

Improved animal diets for oral administration are provided which include a quantity of non-hydrolyzed, non-digested, naturally occurring protein supplemented with a minor amount of an additive selected from the group consisting of di- and tripeptides including an essential amino acid residue. The diets commonly include at least about 8% by weight of such intact protein, which may be derived from typical plant or animal sources. The preferred additive includes an essential amino acid residue selected from the group consisting of lysine, methionine, threonine, tryptophan, isoleucine and valine. Use of the di-and tripeptide additives of the invention gives increased nitrogen use by the animal, as compared with feeding of the amino acid constituents of the additives.

RELATED APPLICATION

This is a continuation-in-part application of Ser. No. 08/035,600, filedMar. 23, 1993, now U.S. Pat. No. 5,374,428.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is broadly concerned with improved diets for oraladministration comprising intact, non-hydrolyzed, non-digested,naturally occurring protein(s) supplemented with a minor amount of anadditive selected from the group consisting of di- and tripeptideshaving at least one essential amino acid residue. More particularly, itis concerned with such diets, and corresponding feeding methods, whereinthe presence of di- or tripeptide additive results in greaterutilization of amino acid nitrogen by the animal, allowing correspondingreductions in the protein content of the diets.

2. Description of the Prior Art

Presently, most essential amino acids supplied by animal diets arederived from naturally occurring plant or animal proteins. It is known,however, to supplement normal diets with various free amino acids suchas lysine from lysine.sup.. HCl, DL-methionine, L-tryptophan,L-isoleucine and L-threonine. The theory of such supplementation is thatthe free amino acids are thought to be absorbed by an animal morereadily than more complex peptides and proteins. For example, theaddition of lysine.sup.. HCl to a ton of swine finishing feed allows thedietary protein content to be reduced from 14% to 12%, by replacing 100pounds of soybean meal with 97 pounds of corn and 3 pounds oflysine.sup.. HCl.

Peptides can be produced by enzymatic digestion of protein withproteinases or peptidases. Typically, the digestive process involves theenzymatic degradation of dietary proteins to free amino acids orpeptides of varying chain lengths. Research has been conducted in thepast to evaluate the nutritional value of dietary peptide supplements inthe form of protein hydrolysate peptides, which are a mixture of manyamino acids found in proteins prior to hydrolysis thereof. Suchexperiments have been carried out in many species, including man androdents. Additionally, studies have been carried out in many species toevaluate the absorptive potential and mechanism of utilization for aminoacids and peptides, including man, rodents, fowl, ruminants, and severalaquatic species. These studies involve infusion of peptides into thedigestive system of the test species, or in vitro digestiveinvestigations.

SUMMARY OF THE INVENTION

The present invention pertains to new animal diets designed for oraladministration (feeding) supplemented with a minor amount of an additiveselected from the group consisting of di- and tripeptides having atleast one essential amino acid residue (i.e., a residue of methionine,arginine, threonine, tryptophan, histidine, isoleucine, lysine, leucine,valine or phenylalanine). The diets of the invention include a quantityof nonhydrolyzed, non-digested, naturally occurring proteins, such asthose typically derived from plant and animal sources. In addition, thedi- and tripeptides do not compete for the same transport mechanism asthe free amino acid constituents thereof. Accordingly, use of theadditives of the invention permits better utilization of nitrogen by theanimal, thereby allowing concomitant reduction in more expensivenaturally occurring protein sources in the diets.

In more detail, the preferred additive of the invention is a di- ortripepride containing an essential amino acid residue selected from thegroup consisting of lysine, methionine, threonine, tryptophan,isoleucine and valine. The additives may be in the free form, or moreusually in salt form. Generally, the additive is present in a given dietat a level of from about 0.001-5% by weight, and more preferably fromabout 0.01-1% by weight.

The protein forming a part of the diets of the invention can be takenfrom a wide variety of sources, but typically plant protein is present.Such plant protein may be derived from a cereal grain, e.g., corn,soybean, wheat, sorghum, oat and barley. Additionally, the protein canbe wholly or partially derived from animal sources such as meat, bloodmeal or bone meal. The total protein content of the diets is generallyat least about 8% by weight, and more preferably from about 12-50% byweight. Of course, the precise protein content utilized, as well asother nutritionally useful ingredients (e.g., soybean oil or whey)depends upon the animal being fed.

The diets hereof may be formulated for a wide variety of animals, e.g.,swine, poultry, ruminants, domestic pets such as dogs and cats, andfish. Human diets can also be supplemented using the additives of theinvention.

Normally, the diets hereof are fed on an ad libitum basis, but thoseskilled in the art will recognize that this is not a prerequisite. It isonly necessary that a given feed be provided containing non-hydrolyzed,non-digested, naturally occurring protein and be supplemented with a di-or tripeptide as defined above.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following example describes a swine feeding test using a preferreddipeptide in accordance with the invention, namely L-lysyl-glycine.sup..HCl in the context of supplementation of an otherwise normalcorn-soybean meal swine diet. The dipeptide-supplemented diet iscompared with a control, and a diet containing lysine.sup.. HCl and theresults of the test demonstrate that the dipeptide-supplemented dietgave more efficient nitrogen utilization. It is to be understood thatthis example is provided by way of illustration only, and nothingtherein is to be taken as an overall limitation upon the scope of theinvention.

EXAMPLE

A trial of 180 (21±2 days of age) pigs was used in a growth assay tocompare the effects of supplementing the pigs' diet with L-lysine.sup..HCl, 98% (78.5% lysine), and the dipeptide L-lysyl-glycine.sup.. HCl(approximately 50% lysine) on starter pig performance and nitrogenutilization. Pigs were blocked (n=5) by initial weight (6.3 kg) andassigned to treatments according to ancestry and sex. Feed and waterwere available ad libitum for 21 days post-weaning (11.7 kg finalweight). The control diets were formulated to include 0.9% and 1.1%lysine respectively, using a corn-soybean meal mixture containing 15%edible grade dried whey. Synthetic lysine.sup.. HCl and the dipeptidelysyl-glycine were added to the control diets to form test dietscontaining 1.0% and 1.1% lysine and lysyl-glycine respectively. Thefollowing table sets forth each of the six diets used in this study.

                                      TABLE 1                                     __________________________________________________________________________    Composition of Experimental Diets (as-fed)                                                Supplement Source:                                                            Corn-Soybean Meal                                                             Control Diet                                                                            Lysine.HCl                                                                              Lysyl-glycine                                 Item  Lysine, %                                                                           .90  1.10 1.00 1.10 1.00 1.10                                     __________________________________________________________________________    Corn        56.03                                                                              49.23                                                                              56.03                                                                              56.03                                                                              56.03                                                                              56.03                                    Soybean meal, 48%                                                                         19.83                                                                              26.79                                                                              19.83                                                                              19.83                                                                              19.83                                                                              19.83                                    Dried whey  15.00                                                                              15.00                                                                              15.00                                                                              15.00                                                                              15.00                                                                              15.00                                    Soybean oil 4.00 4.00 4.00 4.00 4.00 4.00                                     Monocalcium phosphate                                                                     1.91 1.79 1.91 1.91 1.91 1.91                                     Limestone   .80  .77  .80  .80  .80  .80                                      Salt        .30  .30  .30  .30  .30  .30                                      Premix                                                                        Vitamins    .25  .25  .25  .25  .25  .25                                      Trace minerals                                                                            .15  .15  .15  .15  .15  .15                                      Selenium    .05  .05  .05  .05  .05  .05                                      Apramycin   1.00 1.00 1.00 1.00 1.00 1.00                                     Copper sulfate                                                                            .08  .08  .08  .08  .08  .08                                      Supplements                                                                   Dl-methionine, 99%                                                                        .05  .01  .05  .05  .05  .05                                      L-threonine .04  --   .04  .04  .04  .04                                      L-lysine.HCl, 98%                                                                         --   --   .13  .25  --   --                                       L-lysyl-glycine                                                                           --   --   --   --   .20  .40                                      Glycine     .20  --   .20  .20  .10  --                                       Corn starch .31  .58  .18  .06  .21  .11                                      Total       100.00                                                                             100.00                                                                             100.00                                                                             100.00                                                                             100.00                                                                             100.00                                   __________________________________________________________________________

Results of growth performance from 0-21 days post-weaning are set forthin Table 2 below. Serum samples were obtained on days 7, 14, and 21 foranalysis of urea nitrogen. Data were analyzed as a randomized completeblock design and means were separated using Bonferroni pared t-tests.Single df contrasts were used to evaluate differences between the twolysine sources and levels. No differences in daily gain or daily feedintake were observed between treatments. In general, pigs consuming the1.1% lysine corn-soybean meal control diet had higher urea nitrogen thanthe pigs consuming the reduced protein diets and those consuming the1.1% lysine, lysyl-glycine supplemented diet had the lowest ureanitrogen. Pigs consuming the diets containing lysyl-glycine had lowerurea nitrogen levels than pigs fed the lysine.sup.. HCl diets on day 21.In summary, differences in growth were not observed between the dietarylysine sources or levels; however, amino acids appeared to be moreefficiently utilized when supplied from the dipeptide lysyl-glycinerather than lysine.sup.. HCl as evidenced by the lower serum ureanitrogen levels on day 21.

                  TABLE 2                                                         ______________________________________                                                 Corn-                                                                         Soybean             Lysyl-                                                    Control Diets                                                                          Lysine HCl glycine                                          Lysine, %: .9      1.1    1.0   1.1  1.0  1.1  SE                             ______________________________________                                        Daily gain, g                                                                            248     270    276   253  218  280  16                             Daily feed, g                                                                            417     418    460   413  395  432  18                             Gain/feed  593.sup.yz                                                                            646.sup.y                                                                            600.sup.yz                                                                          613.sup.yz                                                                         547.sup.z                                                                          643.sup.y                                                                          16                             d 7 urea N, mg/dl                                                                        11.0.sup.yz                                                                           14.0.sup.y                                                                           9.5.sup.z                                                                           9.2.sup.z                                                                          9.7.sup.z                                                                          8.5.sup.z                                                                          .7                             d 14 urea N,                                                                             12.5.sup.y                                                                            13.6.sup.y                                                                           9.6.sup.z                                                                           8.4.sup.z                                                                          8.9.sup.z                                                                          8.6.sup.z                                                                          .6                             mg/dl                                                                         d 21 urea N,                                                                             12.3.sup.x                                                                            13.0.sup.x                                                                           10.7.sup.xy                                                                         8.5.sup.yz                                                                         9.1.sup.yz                                                                         7.9.sup.z                                                                          .5                             mg/dl.sup.a                                                                   ______________________________________                                         .sup.a Contrast of lysine.HCl vs. lysylglycine (P = 0.05)                     .sup.xyz Means within a row lacking a common superscript letter differ (P     < 0.05)                                                                  

We claim:
 1. In a method of feeding an animal selected from the groupconsisting of swine, poultry, dogs, cats and fish, including the stepsof feeding to the animal a diet including from about 12-50% by weight ofa non-hydrolyzed, non-digested, naturally occurring protein, theimprovement which comprises supplementing said diet with from about0.001-5% by weight of an additive selected from the group consisting ofdi- and tripeptides utilizable by said animal and having an essentialamino acid residue selected from the group consisting of methionine,arginine, threonine, tryptophan, histidine, isoleucine, lysine, leucine,valine and phenylalanine.
 2. The method of claim 1, where said essentialamino acid residue is selected from the group consisting of lysine,methionine, threonine, tryptophan, isoleucine and valine.
 3. The methodof claim 1, where another of the amino acid residues of said additive isselected from the group consisting of methionine, threonine, tryptophanand valine.
 4. The method of claim 1, said additive being present in anamount of from about 0.01-1% by weight.
 5. The method of claim 1, atleast a portion of said non-hydrolyzed, non-digested, naturallyoccurring protein being derived from a plant source.
 6. The method ofclaim 5, said plant source being a cereal grain.
 7. The method of claim6, said cereal grain being selected from the group consisting of corn,soybean, wheat, sorghum, oat and barley.
 8. In a method of feeding ananimal selected from the group consisting of swine, poultry, and fish,including the steps of feeding to the animal a diet including from about12-50% by weight of a non-hydrolyzed, non-digested, naturally occurringprotein, the improvement which comprises supplementing said diet withfrom about 0.001-5% by weight of an additive selected from the groupconsisting of di- and tripeptides utilizable by said animal and havingan essential amino acid residue selected from the group consisting ofmethionine, arginine, threonine, tryptophan, histidine, isoleucine,lysine, leucine, valine and phenylalanine.
 9. The method of claim 8,where said essential amino acid residue is selected from the groupconsisting of lysine, methionine, threonine, tryptophan, isoleucine andvaline.
 10. The method of claim 8, where another of the amino acidresidues of said additive is selected from the group consisting ofmethionine, threonine, tryptophan and valine.
 11. The method of claim 8,said additive being present in an amount of from about 0.01-1% byweight.
 12. The method of claim 8, at least a portion of saidnon-hydrolyzed, non-digested naturally occurring protein being derivedfrom a plant source.
 13. The method of claim 12, said plant source beinga cereal grain.
 14. The method of claim 13, said cereal grain beingselected from the group consisting of corn, soybean, wheat, sorghum, oatand barley.
 15. A diet for oral administration to an animal selectedfrom the group consisting of swine, poultry and fish, said dietcomprising from about 12-50% by weight non-hydrolyzed, non-digested,naturally occurring protein supplemented with from about 0.001-5% byweight of an additive selected from the group consisting of di- andtripeptides utilizable by said animal and having an essential amino acidresidue selected from the group consisting of lysine, methionine,threonine, tryptophane, isoleucine, valine, arginine, leucine,phenylalanine and histidine.
 16. A diet for oral administration to ananimal selected from the group consisting of swine, poultry, dogs, catsand fish, said diet comprising from about 12-50% by weightnon-hydrolyzed, non-digested, naturally occurring protein supplementedwith from about 0.001-5% by weight of an additive selected from thegroup consisting of di- and tripeptides utilizable by said animal andhaving an essential amino acid residue selected from the groupconsisting of lysine, methionine, threonine, tryptophane, isoleucine,valine, arginine, leucine, phenylalanine and histidine.